ACE722A 2A 3MHz 6V Synchronous Buck Converter Description The ACE722A is a high-efficiency synchronous, buck DC/DC converter. Its input voltage range is from 2.6V to 6V and provides an adjustable regulated output voltage from 0.6V to Vin while delivering up to 2A of output current. The internal synchronous switches increase efficiency and eliminate the need for an external Schottky diode. It runs at a fixed 3MHz frequency, which allows the use of small inductor with L<1uH while maintaining a high efficiency and small output voltage ripple. When Mode pin is connected to Gnd, the ACE722A is operating in PFM/PWM auto-switch mode which enhance the efficiency at light-load. The ACE722A is available in DFN2x2-8L and SOT-23-5 packages. Features Adjustable Output Voltage, Vfb=0.6V Maximum output current is 2A Range of operation input voltage: Max 6V Standby current: 30uA (typ) Line regulation: 0.1%/V (typ) Load regulation: 10mV (typ) High efficiency, up to 96% Environment Temperature: -20℃〜85℃ Application Power Management for 3G modem Smart Phone Table PC Set Top Box Other Battery Powered Device Absolute Maximum Rating Parameter Value Max Input Voltage 6V Max Operating Junction Temperature(Tj) 125 Ambient Temperature(Ta) -20℃~85℃ Pacage Thermal Resistance (Θ jc) DFN2x2-8L 25℃/W Power Dissipation SOT-23-5 250mW Storage Temperature(Ts) -40℃-150℃ Lead Temperature & Time 260℃,105 ESD (HBM) >2000V Note: Exceed these limits to damage to the device. Exposure to absolute maximum rating conditions may affect device reliability. VER 1.2 1 ACE722A 2A 3MHz 6V Synchronous Buck Converter Packaging Type DFN2x2-8 SOT-23-5 Ordering information ACE722A XX + H Halogen - free Pb - free BN : SOT-23-5 DN: DFN2*2-8 SOT23-5 2 DFN2* 2-8 1 3 NAME DESCRIPTION PGND Power Ground. Bypass with a 10uF ceramic capacitor to PVIN 2 SW 3 AGND Inductor Connection. Connect an inductor Between SW and the regulator output. Analog Ground, Connect to PGND 5 4 FB Feedback Input. Connect an external resistor divider from the output to FB and GND to set the output to a voltage between 0.6V and VIN 1 5 EN Enable pin for the IC. Drive this pin to high to enable the part, low to disable. 6 MODE When forced high, the device operates in fixed frequency PWM mode. When forced low, it enables the power Save Mode with automatic transition from PFM mode to fixed frequency PWM mode. This pin must be terminated. 7 AVIN Analog Power. Short externally to PVIN 8 PVIN Supply Voltage. Bypass with a 10uF ceramic capacitor to PGND 4 VER 1.1 2 ACE722A 2A 3MHz 6V Synchronous Buck Converter BLOCK DIAGRAM Recommended Work Condition Parameter Input Voltage Range Operating Junction Temperature(Tj) Value Max. 6V -20℃-125℃ VER 1.1 3 ACE722A 2A 3MHz 6V Synchronous Buck Converter Electrical Characteristics (VIN =5, TA=25℃) Symbol VDD UVLO Parameter Conditions Input Voltage Range Increase Vin Vref Feedback Voltage Vin=5V, Ven=5V lfblk Feedback Leakage current Quiescent Current Typ 2.6 Input Under Voltage Lockout Iq Min 2.1 0.58 8 Max Unit 6 V 2.2 V 0.6 0.612 V 0.01 0.1 uA Active, Vfb=0.65, No Switching 30 Shutdown 0.1 uA 1 uA LnReg Line Regulation Vin=2.7V to 5.5V 0.04 %/V LdReg Load Regulation Iout=0.01 to 2A 0.15 Fsoc Switching Frequency 2.4 3 3.6 %/A MHz RdsonP PMOS Rdson Lsw=200mA 100 120 Mohm RdsonN NMOS Rdson Lsw=200mA 80 100 mohm Ilimit Peak Current Limit Iswlk SW Leakage Current 2.5 3 Vout=5.5V, EN=GND Venh,Vmdh EN/MODE High Threshold Venl,Vmdl EN/MODE Low Threshold Ienlk,Imdlk EN/MODE Leakage Current EN=MODE=GND Rdischarge Discharge Resistance EN=GND A 10 uA 1.5 V 0.4 180 V 300 1 uA 450 Ohm Typical Application Circuit ACE722A VER 1.1 4 ACE722A 2A 3MHz 6V Synchronous Buck Converter TYPICAL PERFORMANCE CHARACTERISTICS (Vin=3.6V, L=1uH, Cin=10uF, TA=25℃, unless otherwise stated) Efficiency at Vout=3.3V Efficiency at Vout=1.2V Efficiency at Vout=1.8V Load Regulation at Vout=1.8V VER 1.1 5 ACE722A 2A 3MHz 6V Synchronous Buck Converter Switching waveform Vin=3.6V, Vout=1.2V Iout=0A Switching waveform Vin=5V, Vout=3.3V, Iout=0A Load Transient Vin=3.6V, Vout=1.2V, Iout=0.2A/1A Switching waveform Vin=3.6V, Vout=1.2V Iout=0.7A Switching waveform Vin=5V, Vout=3.3V, Iout=0.5A Load Transient Vin=3.6V, Vout=1.8V, Iout=0.2A/1.5A VER 1.1 6 ACE722A 2A 3MHz 6V Synchronous Buck Converter VER 1.1 7 ACE722A 2A 3MHz 6V Synchronous Buck Converter FUNCTIONAL DECRIPTIONS The ACE722A high-efficiency switching regulator is a small, simple, DC-to-DC step-down converter capable of delivering up to 2A of output current. The device operates in pulse-width modulation (PWM) at 3MHz from a 2.6V to 5.5V input voltage and provides an output voltage from 0.6V to VIN, making the ACE722A ideal for on-board post-regulation applications. An internal synchronous rectifier improves efficiency and eliminates the typical Schottky free-wheeling diode. Using the on resistance of the internal high-side MOSFET to sense switching currents eliminates current-sense resistors, further improving efficiency and cost. Load Operation ACE722A uses a PWM current-mode control scheme. An open-loop comparator compares the integrated voltage-feedback signal against the sum of the amplified current-sense signal and the slope compensation ramp. At each rising edge of the internal clock, the internal high-side MOSFET turns on until the PWM comparator terminates the on cycle. During this on-time, current ramps up through the inductor, sourcing current to the output and storing energy in the inductor. The current mode feedback system regulates the peak inductor current as a function of the output voltage error signal. During the off cycle, the internal high-side P-channel MOSFET turns off, and the internal low-side N-channel MOSFET turns on. The inductor releases the stored energy as its current ramps down while still providing current to the output. Current Sense An internal current-sense amplifier senses the current through the high-side MOSFET during on time and produces a proportional current signal, which is used to sum with the slope compensation signal. The summed signal then is compared with the error amplifier output by the PWM comparator to terminate the on cycle. Current Limit There is a cycle-by-cycle current limit on the high-side MOSFET. When the current flowing out of SW exceeds this limit, the high-side MOSFET turns off and the synchronous rectifier turns on. ACE722A utilizes a frequency fold-back mode to prevent overheating during short-circuit output conditions. The device enters frequency fold-back mode when the FB voltage drops below 200mV, limiting the current to IPEAK and reducing power dissipation. Normal operation resumes upon removal of the short-circuit condition. Soft-start ACE722A has a internal soft-start circuitry to reduce supply inrush current during startup conditions. When the device exits under-voltage lockout (UVLO), shutdown mode, or restarts following a thermal-overload event, the l soft-start circuitry slowly ramps up current available at SW. VER 1.1 8 ACE722A 2A 3MHz 6V Synchronous Buck Converter UVLO and Thermal Shutdown If VIN drops below 2V, the UNLO circuit inhibits switching. Once VIN rises 2.1V, the UVLO clears, and the soft-start sequence a activates. Thermal-overload protection limits total power dissipation in the device. When the junction temperature exceeds TJ=+160℃, a thermal sensor forces the device into shutdown, allowing the die to cool. The thermal sensor turns the device on again after the junction temperature cools by 15℃, resulting in a pulsed output during continuous overload conditions. The soft-start sequence begins. DESIGN PROCEDURE INDUCTOR SELECTION The peak-to-peak ripple is limited to 30% of the maximum output current. This places the peak current far enough from the minimum overcurrent trip level to ensure relible operation while providing enough current ripples for the current mode converter to operate stably. In this case, for 2A maximum output current, the maximum inductor ripple current is 667 mA. The inductor size is estimated as following equation: LIDEAL=(VIN(MAX)-VOUT)/IRIPPLE*DMIN8*DMIN*(1/FOSC) Therefore, for VOUT=1.8V, The inductor values is calculated to be L=0.60uH. Choose 1uH And for VOUT=1.2V, The inductor values is calculated to be L=0.469uH. Choose 0.47uH The resulting ripples is IRIPPLE=(VIN(MAX)- VOUT)/LACTUAL*DMIN*(1/FOSC) When, VOUT=1.8V,IRIPPLE=403mA VOUT=1.2 V,IRIPPLE=665mA Output Capacitor Selection For mos applications a nominal 10uF or 22 uF capacitor is suitable. The ACE722A internal compensation is designed for a fixed corner frequency that is equal to 1 FC= 1 2∗ π√COUT∗ L = 50Khz For example, for VOUT=1.8V, L=1uH, COUT=10uF, for VOUT=1.2V, L=0.47uH, COUT=22uF Setting Output Voltage Output voltages are set by external resistors. The FB_threshold is 0.6V. RTOP=RBOTTOMX〔 （VOUT/0.6）-1〕 VER 1.1 9 ACE722A 2A 3MHz 6V Synchronous Buck Converter Guidelines for input Capacitor and Output Capacitor The input capacitor in a DC-to-DC converter reduces current peaks drawn from the battery or other input power source and reduces switching noise in the controller. The impedance of the input capacitor at the switching frequency should be less than that of the input source so high-frequency switching currents do not pass through the input source. The output capacitor keeps output ripple small and ensures control-loop stability. The output capacitor must also have low impedance at the switching frequency. Ceramic, polymer, and tantalum capacitors are suitable, with ceramic exhibiting the lowest ESR and high-frequency impedance. Output ripple with a ceramic output capacitor is approximately as follows: RRIPPLE=IL(PEAK)〔1/（2 X FOSC X COUT）〕 If the capacitor has significant ESR, the output ripple component due to capacitor ESR is follows: VRIPPLE(ESR)=IL(PEAK) X ESR VER 1.1 10 ACE722A 2A 3MHz 6V Synchronous Buck Converter Packing Information DFN2X2-8L SOT-23-5 VER 1.1 11 ACE722A 2A 3MHz 6V Synchronous Buck Converter Notes ACE does not assume any responsibility for use as critical components in life support devices or systems without the express written approval of the president and general counsel of ACE Electronics Co., LTD. As sued herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and shoes failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user. 2. A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness. ACE Technology Co., LTD. http://www.ace-ele.com/ VER 1.1 12